Chuck Bednar for redOrbit.com – @BednarChuck
A dwarf galaxy recently discovered orbiting the Milky Way appears to be radiating gamma rays, and leading researchers from Brown and Carnegie Mellon universities hypothesize that it could be filled with particles of the mysterious substance known as dark matter.
The galaxy in question in named Reticulum 2, and it was discovered as part of the ongoing Dark Energy Survey. Reticulum 2 is located just 98,000 light-years away, making it one of the closest dwarf galaxies ever located and a prime candidate to search for dark matter – invisible particles believed to account for as much as 85 percent of the mass in the known universe.
As Discovery News explains, by observing the spin of galaxies and the interactions that take place within galactic clusters, astronomers have noticed that there is an invisible type of matter that exerts a powerful gravitational pull on the space around it. However, since it does not interact with normal matter in this way, it cannot be directly seen, and little is known about it.
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A wimpy source of dark matter
One hypothesis suggests that weakly interacting massive particles (WIMPS) are the source of dark matter, the website noted. When they collide, it is believed that they will annihilate, leaving energy in the form of gamma rays as one of their byproducts. WIMPS have yet to be discovered, though, and scanning the universe for gamma rays generated by these particles has proven to be extremely difficult, as many other phenomena in the universe also emit this radiation.
While black holes and pulsars are among the known sources of gamma rays, those entities are typically not abundant in dwarf galaxies, making them excellent places to conduct searches for these dark matter-related signals. They have detected radiation originating from the vicinity of Reticulum 2, and the presence of a potential source of WIMP annihilation so close to Earth has the scientists cautiously optimistic.
“Something in the direction of this dwarf galaxy is emitting gamma rays,” lead author Alex Geringer-Sameth, a postdoctoral research associate at Carnegie Mellon’s Department of Physics, said in a statement Tuesday. “There’s no conventional reason this galaxy should be giving off gamma rays, so it’s potentially a signal for dark matter.”
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“The gravitational detection of dark matter tells you very little about the particle behavior of the dark matter,” added Matthew Walker, assistant professor of physics and a member of CMU’s McWilliams Center for Cosmology. “But now we may have a non-gravitational detection that shows dark matter behaving like a particle, which is a holy grail of sorts.”
Astronomers have been studying dwarf galaxies for several years, using NASA’s Fermi Gamma-ray Space Telescope to hunt for signals of the radiation. Recently, Geringer-Sameth, Walker, and their colleagues have been developing a technique that searches for weak signals in the gamma ray data that could be attributed to dark matter annihilation.
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